Perceiving affordances in virtual reality: influence of person and environmental properties in perception of standing on virtual grounds

We evaluated the perception of affordances in virtual environments (VE). In our work, we considered the affordances for standing on a virtual slanted surface. Participants were asked to judge whether a virtual slanted surface supported upright stance. The objective was to evaluate whether this perception was possible in virtual reality (VR) and comparable to previous works conducted in real environments. We found that the perception of affordances for standing on a slanted surface in virtual reality is possible and comparable (with an underestimation) to previous studies conducted in real environments. We also found that participants were able to extract and to use virtual information about friction in order to judge whether a slanted surface supported an upright stance. Finally, results revealed that the person’s position on the slanted surface is involved in the perception of affordances for standing on virtual grounds. Taken together, our results show quantitatively that the perception of affordances can be effective in virtual environments and influenced by both environmental and person properties. Such a perceptual evaluation of affordances in VR could guide VE designers to improve their designs and to better understand the effect of these designs on VE users.     

Training in virtual environments: transfer to real world tasks and equivalence to real task training

Virtual environments (VEs) are extensively used in training but there have been few rigorous scientific investigations of whether and how skills learned in a VE are transferred to the real world. This research aimed to measure and evaluate what is transferring from training a simple sensorimotor task in a VE to real world performance. In experiment 1, real world performances after virtual training, real training and no training were compared. Virtual and real training resulted in equivalent levels of post-training performance, both of which significantly exceeded task performance without training. Experiments 2 and 3 investigated whether virtual and real trained real world performances differed in their susceptibility to cognitive and motor interfering tasks (experiment 2) and in terms of spare attentional capacity to respond to stimuli and instructions which were not directly related to the task (experiment 3). The only significant difference found was that real task performance after training in a VE was less affected by concurrently performed interference tasks than was real task performance after training on the real task. This finding is discussed in terms of the cognitive load characteristics of virtual training. Virtual training therefore resulted in equivalent or even better real world performance than real training in this simple sensorimotor task, but this finding may not apply to other training tasks. Future research should be directed towards establishing a comprehensive knowledge of what is being transferred to real world performance in other tasks currently being trained in VEs and investigating the equivalence of virtual and real trained performances in these situations.     

Training in virtual environments: transfer to real world tasks and equivalence to real task training

Virtual environments (VEs) are extensively used in training but there have been few rigorous scientific investigations of whether and how skills learned in a VE are transferred to the real world. This research aimed to measure and evaluate what is transferring from training a simple sensorimotor task in a VE to real world performance. In experiment 1, real world performances after virtual training, real training and no training were compared. Virtual and real training resulted in equivalent levels of post-training performance, both of which significantly exceeded task performance without training. Experiments 2 and 3 investigated whether virtual and real trained real world performances differed in their susceptibility to cognitive and motor interfering tasks (experiment 2) and in terms of spare attentional capacity to respond to stimuli and instructions which were not directly related to the task (experiment 3). The only significant difference found was that real task performance after training in a VE was less affected by concurrently performed interference tasks than was real task performance after training on the real task. This finding is discussed in terms of the cognitive load characteristics of virtual training. Virtual training therefore resulted in equivalent or even better real world performance than real training in this simple sensorimotor task, but this finding may not apply to other training tasks. Future research should be directed towards establishing a comprehensive knowledge of what is being transferred to real world performance in other tasks currently being trained in VEs and investigating the equivalence of virtual and real trained performances in these situations.     

Evaluation of Internal and External Validity of a Virtual Environment for Learning a Long Procedure

Virtual reality is a frequently used tool in vocational training. Nevertheless, its efficiency has not been systematically tested. The main goal of this study is to assess the effectiveness of a virtual environment (VE) for learning a complex procedure in the biomedical domain. Two experiments were performed. The first one assessed internal validity of the VE, which is the effectiveness of using a VE in the process of learning a new procedure. The second one tested external validity of the VE, which is the participants’ ability to reproduce the acquired skills in a real context. We find that internal and external validity must be evaluated before using a virtual environment in long-term procedure learning. The results of such evaluations are a basis for future experiments aiming to optimize learning conditions in a VE and transferring the acquired skills in a real context.     

Natural perspective projections for head-mounted displays

The display units integrated in today's head-mounted displays (HMDs) provide only a limited field of view (FOV) to the virtual world. In order to present an undistorted view to the virtual environment (VE), the perspective projection used to render the VE has to be adjusted to the limitations caused by the HMD characteristics. In particular, the geometric field of view (GFOV), which defines the virtual aperture angle used for rendering of the 3D scene, is set up according to the display field of view (DFOV). A discrepancy between these two fields of view distorts the geometry of the VE in a way that either minifies or magnifies the imagery displayed to the user. It has been shown that this distortion has the potential to affect a user's perception of the virtual space, sense of presence, and performance on visual search tasks. In this paper, we analyze the user's perception of a VE displayed in a HMD, which is rendered with different GFOVs. We introduce a psychophysical calibration method to determine the HMD's actual field of view, which may vary from the nominal values specified by the manufacturer. Furthermore, we conducted two experiments to identify perspective projections for HMDs, which are identified as natural by subjects--even if these perspectives deviate from the perspectives that are inherently defined by the DFOV. In the first experiment, subjects had to adjust the GFOV for a rendered virtual laboratory such that their perception of the virtual replica matched the perception of the real laboratory, which they saw before the virtual one. In the second experiment, we displayed the same virtual laboratory, but restricted the viewing condition in the real world to simulate the limited viewing condition in a HMD environment. We found that subjects evaluate a GFOV as natural when it is larger than the actual DFOV of the HMD--in some cases up to 50 percent--even when subjects viewed the real space with a limited field of view.     

Agent技术在虚拟企业创建过程中的应用研究

虚拟企业（virtual enterprise，VE）被认为是21世纪最有竞争力的企业运行模式，它面向全球范围的企业资源，通过构建VE的联盟之间的快速重组，实现联盟企业之间的敏捷化和柔性化。如何选择伙伴企业，则是VE创建过程中的关键。文章首先采用了分布式对象技术以支持VE创建时的需要；然后提取了用于伙伴企业选择的Agent基本属性；规划了伙伴企业选择过程；最后用多Agent技术为VE构建一个支持动态联盟的多Agent远程制造系统。     

虚拟环境中的视觉感知

通过对现实世界,平面图像的视觉成象方式的比较,指出虚拟环境成象方式是二者相结合的产物。在论述虚拟环境所提供的视差对三维深度感知重要性的同时,结合视觉生理特点,分析总结了虚拟环境所具有的缺陷,即违背了视标所发出的入瞳光线的散开度与双眼所处的状态应该相辅相成这一规律,提出了虚拟环境给队造成头晕、眼睛疲劳等不良反应的根源是虚拟对象容易使双眼的辐辏和调节功能发生冲突。最后列举并分析了刷新延迟、分辩率、瞳距等各种可能给观察者带来不良反应的诸多因素。     

A multiagent-based complex systems approach for dynamic negotiation mechanism in virtual enterprise

Nowadays a sophisticated match-making mechanism is necessary for appropriate collaborations in virtual enterprise (VE). Virtual market based match-making operation enables effective partner search in terms of products allocation by distributing the scheduled resources according to the market prices, which define common scale of value across the various products. We formulate the VE match-making model as discrete resource allocation problem, and propose a complex market-oriented programming framework based on the economics of complex systems. Three types of heterogeneous agents are defined in the complex virtual market. It is described that their interactions with micro behaviour emerge a macro order of the virtual market, and the clearing price dynamism can be analysed in economic terms. The applicability of the framework into resource allocation problem for VE is also discussed.     

Intelligent Cruise-Control Navigation: A new navigation/travel method for use in virtual environments

An important feature of virtual reality is the facility for the user to move around a virtual environment in a natural and easily controlled manner. Navigation, also called locomotion, travel or motion, involves changing the perspective of the user in the virtual environment (VE). It allows the user to move in the VE as well as reorient themselves to look at the world differently. Natural locomotion methods are able to contribute to a sense of presence and reality. The illusion of presence can be lost through unnatural experiences during travel in the VE. This can be caused by poor interactive metaphors or by experiences which do not agree with the user's everyday understanding of the real world. This paper focuses on the navigation method in the VE, one of the major interfaces for the interactivity between human and VE in virtual reality circumstances and worlds. It proposes a new navigation method. Intelligent Cruise-Control Navigation (ICCN), which provides a natural and user-centred approach to navigation in the VE and can improve the user's sense of reality and presence. ICCN is composed of three major phases: Constant Velocity Navigation, Collision Detection and Avoidance, and Path Adjustment. The ICCN can reduce the user's fatigue and improve the user's presence in the VE. The small experimental study reported in this paper suggests that the ICCN will be a natural, straightforward, and useful navigation interface in VE.     

Driving simulation: challenges for VR technology

Virtual driving environments represent a challenging test for virtual reality technology. We present an overview of our work on the problems of scenario and scene modeling for virtual environments (VEs) in the context of the Iowa Driving Simulator (IDS). The requirements of driving simulation-a deterministic real-time software system that integrates components for user interaction, simulation, and scenario and scene modeling-make it a valuable proving ground for VE technologies. The goal of our research is not simply to improve driving simulation, but to develop technology that benefits a wide variety of VE applications. For example, our work on authoring high-fidelity VE databases and on directable scenarios populated with believable agents also targets applications involving interaction with simulated, walking humans and training in the operation of complex machinery. This work has benefited greatly from the experience of developing components for a full-scale operational VE system like IDS, and we believe that many other proposed VE technologies would similarly benefit from such real-world testing     

基于多智能体的虚拟企业任务调度模型及优化

采用多智能体技术构建虚拟企业任务调度模型, 并对基于该模型的任务调度运作过程进行说明. 针对调度优化问题, 以资源智能体承担的生产任务为研究对象, 综合考虑生产任务之间的时序逻辑关系、作业时间及资源自身已确定的生产任务等影响因素, 建立以生产延续时间最小为目标的优化模型, 给出粒子群优化求解算法. 应用实例及数字仿真验证了模型及优化算法有效性.     

Mixed reality: future dreams seen at the border between real andvirtual worlds

Mixed reality (MR) is a kind of virtual reality (VR) but a broader concept than augmented reality (AR), which augments the real world with synthetic electronic data. On the opposite side, there is a term, augmented virtuality (AV), which enhances or augments the virtual environment (VE) with data from the real world. Mixed reality covers a continuum from AR to AV. This concept embraces the definition of MR stated by Milgram and Kishino (1994). We describe some technical achievements we made in the Mixed Reality Project in Japan     

Spatial representations of virtual mazes: the role of visual fidelity and individual differences

Twenty-four people learned three versions of a room-sized maze: a wire-frame desktop virtual environment (VE), a normal surface-rendered desktop VE, and a real-world maze. Differences among the mental representations formed from each environment were measured with pointing and distance estimation tasks in a real-world version of each maze. People were more accurate at pointing after having learned the real and wire-frame VE maze than the surface-rendered VE maze; however, this effect was small compared with the effect of individual differences. Differences in gender, spatial ability, and prior computer experience were significantly related to the ability to acquire spatial information from the desktop VE. There was a high correlation between spatial knowledge when it was measured in the VE and spatial knowledge measured in the real world. Actual or potential applications include the design of effective VE training systems.     

Context-aware workflow management for virtual enterprises based on coordination of agents

Although virtual enterprises (VE) make it possible for small flexible enterprises to form a collaborative network to respond to business opportunities through dynamic coalition and sharing of the core competencies and resources, they also pose new challenges and issues. Creation of VE involves dynamically established partnerships between the partners and relies on a flexible coordination scheme. The dynamic organizations formed in VE present a challenge in the development of a new methodology to dynamically allocate re-sources and deliver the relevant information to the right people at the right time. A key issue is the development of an effective workflow management scheme for VE. Multi-agent systems (MAS) provide a flexible architecture to deal with changes based on dynamic organization and collaboration of autonomous agents. Despite the extensive studies and research results on MAS, development of a design methodology to support coordination and operations is critical to the success and adoption of VE. The objectives of this research are to propose a design methodology to facilitate coordination and development of context-aware workflow management systems and achieve effective resource allocation for VE based on MAS architecture. To achieve these objectives, a scheme for coordination of agents is proposed. Petri net models are used in the coordination scheme to describe workflows and capture resource activities in VE. The interactions between agents lead to a dynamic workflow model for VE. Based on the aforementioned model, we propose architecture to dynamically generate context-aware graphical user interface to guide the users and control resource allocation based on the state of VE. An order management example is used throughout this paper to illustrate the proposed design methodology.     

Predicting real-world ergonomic measurements by simulation in a virtual environment

Virtual reality techniques have been increasingly used for ergonomic applications. However, it is always important to know whether the results obtained in a virtual environment (VE) are representative of a real environment (RE) ones. This paper presents our preliminary experimental results on the relationship between ergonomic measurements in VE and RE for some typical “drilling” tasks. The same tasks were carried out by thirty male manufacturing factory workers in both VE and RE. Five evaluation indices - three objective (elbow angle, maximum force capacity reduction, and task completion time) and two subjective (BPD - Body Part Discomfort and RPE - Rated Perceived Exertion) - were used to evaluate the similarities between VE and RE for the selected “drilling” tasks. Four of these indices (all except elbow angle) were significantly higher (p < 0.05) in VE than in RE, which indicates that subjects experienced more discomfort and grew fatigued more quickly in VE. However, linear correlations (Pearson’s rho: 0.635-0.807) between VE and RE were found for two of the five indices (BPD and maximum force capacity reduction).

Relevance to industry

Using digital mock-ups and virtual reality simulations, industrial work activities can be evaluated to identify potential ergonomic problems during an early design stage, which reduces design time and costs, increases quality and improves customer satisfaction. A validated linear relationship can provide a reference for work design in virtual reality.     

Service-oriented architecture for ontologies supporting multi-agent system negotiations in virtual enterprise

This paper offers a service-oriented architecture (SOA) for ontology-based multi-agent system (MAS) negotiations in the context of virtual enterprises (VEs). The objective of this paper is fourfold. First, it is to design a SOA which utilizes ontology and MAS to provide a distributed and interoperable environment for automated negotiations in VE. In this architecture, individual ontologies for both the VE initiator and its potential partners are constructed to describe and store resources and service knowledge. Second, a series of semantic ontology matching methods are developed to reach agents’ interoperability during the negotiation process. Third, correspondence-based extended contract net protocol is presented, which provides basic guidelines for agents’ reaching mutual understandings and service negotiation. Last, a fuzzy set theory based knowledge reuse approach is proposed to evaluate the current negotiation behaviors of the VE partners. A walkthrough example is presented to illustrate the methodologies and system architecture proposed in this paper.     

Real-time virtual environment signal extraction and denoising using programmable graphics hardware

The sense of being within a three-dimensional (3D) space and interacting with virtual 3D objects in a computer-generated virtual environment (VE) often requires essential image, vision and sensor signal processing techniques such as differentiating and denoising. This paper describes novel implementations of the Gaussian filtering for characteristic signal extraction and wavelet-based image denoising algorithms that run on the graphics processing unit (GPU). While significant acceleration over standard CPU implementations is obtained through exploiting data parallelism provided by the modern programmable graphics hardware, the CPU can be freed up to run other computations more efficiently such as artificial intelligence (AI) and physics. The proposed GPU-based Gaussian filtering can extract surface information from a real object and provide its material features for rendering and illumination. The wavelet-based signal denoising for large size digital images realized in this project provided better realism for VE visualization without sacrificing real-time and interactive performances of an application.     

Responding to a fire emergency in a virtual environment: different patterns of action for different situations

This paper presents an experimental study of participants' response to the sudden appearance of a fire emergency in a virtual environment (VE) and of the adaptivity of their response pattern. A VE has been built in which participants meet two situations: first an explorative navigation and afterwards a hurried escape from the unexpected outbreak of fire. Fire intensity and participants' distance from the exit at the outbreak of fire have been varied as well, to create different degrees of danger and different degrees of difficulty in the task of leaving the premises. Participants' action has been collected automatically for quantitative analysis by registering each individual activation of the interaction devices (a triple button joystick). In addition, the movements in both virtual and real environment of additional groups of participants have been videorecorded for qualitative analysis. Results show that the appearance of the fire emergency triggers important changes in the way people move in the VE, and that such changes are all adaptive responses to an emergency situation. In conclusion, people show recognition of a dangerous situation in a VE and readily produce adaptive responses, making the VE suitable for emergency simulations and for use as an effective training tool.     

Haptic-feedback support for cognitive mapping of unknown spaces by people who are blind

Mental mapping of spaces is essential for the development of efficient orientation and mobility skills. Most of the information required for this mental mapping is gathered through the visual channel. People who are blind lack this information, and in consequence, they are required to use compensatory sensorial channels and alternative exploration methods. In this study, people who are blind use a virtual environment (VE) that provides haptic and audio feedback to explore an unknown space. The cognitive mapping of the space based on the VE and the subject's ability to apply this map to accomplish tasks in the real space are examined. Results show clearly that a robust and comprehensive map is constructed, contributing to successful performance in real space tasks.     

Responding to a fire emergency in a virtual environment: different patterns of action for different situations

This paper presents an experimental study of participants' response to the sudden appearance of a fire emergency in a virtual environment (VE) and of the adaptivity of their response pattern. A VE has been built in which participants meet two situations: first an explorative navigation and afterwards a hurried escape from the unexpected outbreak of fire. Fire intensity and participants' distance from the exit at the outbreak of fire have been varied as well, to create different degrees of danger and different degrees of difficulty in the task of leaving the premises. Participants' action has been collected automatically for quantitative analysis by registering each individual activation of the interaction devices (a triple button joystick). In addition, the movements in both virtual and real environment of additional groups of participants have been videorecorded for qualitative analysis. Results show that the appearance of the fire emergency triggers important changes in the way people move in the VE, and that such changes are all adaptive responses to an emergency situation. In conclusion, people show recognition of a dangerous situation in a VE and readily produce adaptive responses, making the VE suitable for emergency simulations and for use as an effective training tool.